The present invention relates to a method and an apparatus for measuring a scattered light arising when a light is propagated through the inside of a liquid sample to be detected such as a urine.
In conventional, when the scattered light of the solution to be detected is measured, there has been adopted a method in which a projected light is focused in the solution to be detected, and the scattered light arisen in the focused region is condensed onto the photo detective area of a photosensor by an integrating sphere or a lens, and detected to trap the scattered light advancing in all directions is trapped as much as possible. Further, by focusing the projected light to generate the scattered light in a smaller region, it is possible to trap the scattered light at a larger solid angle, i.e., range. Consequently, the power of the scattered light reaching the photosensor can be increased, so that the output signal level from the photosensor can also be increased. Further, there is another advantage in that the signal to noise ratio in an electric circuit can be increased.
However, there are present a large number of paths for the scattered light to reach the photosensor, thereby raising the probability of receiving the obstruction due to suspending particles such as bubbles and dust present in the solution to be detected. Further, if the turbidity of the solution to be detected is increased, the proportional relation between the power of the scattered light reached the photosensor through a path with a long optical path length and the turbidity is deteriorated due to a propagation loss. At the same time, the difference in propagation loss due to the difference in optical path length between respective paths is also increased. Then, a calibration curve of the turbidity and the scattered light power to be detected is distorted, resulting in a reduced dynamic range. Further, the scattered light also tends to be affected by the refractive index of the solution to be detected.
Thus, when the measurement is carried out by increasing the trapping rate of the scattered light, the electric signal to noise ratio is improved, but the optical signal to noise ratio, proportional relation, and reproducibility are deteriorated. Especially, the deterioration in optical characteristics is remarkable for the solution to be detected such as a urine, which has a large difference in refractive index, includes a large number of suspending particles such as bubbles and dust, and largely changes in turbidity due to mixing of a reagent, heating, or the like. In such a case, the comprehensive measured characteristics combining the optical and electric characteristics may be deteriorated.
Further, with the foregoing conventional method aimed at trapping the scattered light as much as possible, a cylindrical sample cell or test tube has been generally used for achieving the ease of the arrangement, and the uniformity of the paths for the scattered light. Then, a light has been made incident from the side of the sample cell or test tube to focus the projected light on the central portion. However, such a configuration has presented a problem that the system for condensing the light emitted from the sample cell is enlarged in size and becomes complicated.
Further, as a conventional method of urinalysis, there has been a method in which a test paper impregnated with a reagent, or the like is dipped in a urine, and a color reaction thereof is observed by means of a spectroscope or the like to detect the components of the urine. The test papers herein used have been disadvantageously required to be individually produced according to respective inspection items such as glucose and protein.
It is therefore an object of the present invention to provide a scattered light measuring method and a scattered light measuring apparatus, which reduce the influences of differences in refractive index and optical light transmittance between respective solutions to be detected, for solving the foregoing prior-art problems.
It is another object of the present invention to provide a method for measuring a scattered light, whereby the influences of the pollutants inside and on the surfaces of an optical window are reduced.
It is a further object of the present invention to provide a method of urinalysis which has high reliability, is easy to maintain and control, and has high practical utility.
The present invention relates to a method for measuring a scattered light arising when a light is propagated through an inside of a solution to be detected, comprising the steps of: allowing a light to be incident upon and propagated from a first optical window into the solution to be detected in a sample cell, which has at least the first optical window and a second optical window; and measuring by a photosensor a scattered light propagating in a direction substantially perpendicular to the propagating direction of the light propagating through the inside of the solution to be detected out of a scattered light arising in the solution to be detected from the second optical window. In this method, it is effective that a surface of the second optical window closer to the solution to be detected is located substantially in parallel to an optical axis of the light propagating through the inside of the solution to be detected.
Further, it is effective that a position Y of the optical axis of the light propagating through the inside of the solution to be detected is set such that the power of a scattered light incident upon the photo detective area of the photosensor out of a scattered light arising from, i.e., inside and on the surfaces of, the second optical window is not more than a predetermined value within a practically allowable range.
Still further, it is effective that a position Y of the optical axis and a position Z of the photosensor are set such that the power of the scattered light incident upon the photo detective area of the photosensor out of the scattered light arising from, i.e., inside and on the surfaces of, the first optical window is not more than a predetermined value within a practically allowable range.
On the other hand, it is effective that the position Z of the photosensor is set such that a scattered light arisen in a region closest to the surface of the first optical window, said surface being closer to (in contact with) the solution to be detected, can be measured.
It is also effective that the position Y of the optical axis is set at a position closest to the surface of the second optical window, said surface being closer to (in contact with) the solution to be detected.
Further, it is effective that the light propagating through the inside of the solution to be detected is a linearly polarized light, and that a scattered light propagating in a direction perpendicular to the polarization direction, which is a vibrating direction of a magnetic field of the light, is measured.
Still further, it is effective that the light to be propagated through the inside of the solution to be detected is a substantially parallel light, and the light is made incident such that the light propagates in a direction perpendicular to the surface of the optical window closer to the solution to be detected.
It is effective that the predetermined value is set by defining the power of a scattered light arising inside and on the surfaces of the second optical window from the proportion of the power of the light propagating inside and on the surfaces of the second optical window out of the power of the light to be propagated through the inside of the solution to be detected.
Further, it is also effective that the predetermined value is set by defining the power of a scattered light arising inside and on the surfaces of the first optical window from the proportion of the power of the light propagating in a region within the first optical window, where a scattered light receivable by the photosensor is generated, out of the power of the light to be propagated through the inside of the solution to be detected.
It is effective that the position Y of the optical axis and the position Z of the photosensor are set such that, under the condition that the first and second optical windows contaminated, the power of a scattered light incident upon the photosensor out of the scattered light arisen at both the first and second optical windows is not more than the predetermined value.
Further, it is also effective that the position Y of the optical axis and the position Z of the photosensor are set such that the power of a scattered light to be measured by using a solution to be detected, which has a minimum refractive index and generates substantially no scattered light, is not more than the predetermined value.
Further, the present invention also relates to a method of urinalysis comprising the steps of: opacifying a urine as a solution to be detected by heating and coagulating a protein in the urine, or by mixing therein a reagent for coagulating the protein, measuring a scattered light arising in accordance with the opacity of the urine with the above-mentioned method for measuring a scattered light, and determining the protein concentration in the solution to be detected from the measured value.
Still further, the present invention relates to a scattered light measuring apparatus, which comprises: a rectangular sample cell having at least two adjacent transparent side walls each functioning as optical window and holding a solution to be detected; a light source for projecting a light into the solution to be detected in a direction perpendicular to the surface, which is in contact with the solution to be detected, of a first optical window of the sample cell through the first optical window; a photosensor for detecting a scattered light arising when the light is propagated through the inside of the solution to be detected, and emitted through a second optical window adjacent to the first optical window; and a detecting angle restricting means for restricting the angle of a scattered light incident upon the photosensor within a predetermined angle centering on a direction perpendicular to the propagating direction of the light to be propagated through the inside of the solution to be detected, wherein a scattered light intensity of the solution to be detected is measured by an output signal from the photosensor.
While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings.